CN111003998B

CN111003998B - Non-ignition self-compacting concrete and preparation method thereof

Info

Publication number: CN111003998B
Application number: CN201911346933.5A
Authority: CN
Inventors: 张林涛; 黄加宝; 孙远松; 邓燚; 张云峰
Original assignee: Chengdu Huge Construction Material Co ltd
Current assignee: Chengdu Huge Construction Material Co ltd
Priority date: 2019-12-24
Filing date: 2019-12-24
Publication date: 2021-08-31
Anticipated expiration: 2039-12-24
Also published as: CN111003998A

Abstract

The invention discloses a preparation method of non-ignition self-compacting concrete, which comprises the following production raw materials of cement, mineral admixture, water, polyacrylonitrile-based carbon fiber, water reducing agent, dolomite coarse aggregate and dolomite fine aggregate; wherein the single mixing amount of the dolomite coarse aggregate is 756-810 kg, and the single mixing amount of the dolomite fine aggregate is 835-859 kg. The advantages are that: the self-compaction of the non-ignition concrete material is obviously improved, and the non-ignition property of the material is further improved.

Description

Non-ignition self-compacting concrete and preparation method thereof

Technical Field

The invention relates to a concrete production technology, in particular to a production method of non-ignition concrete.

Background

With the development of economic society, people pay more attention to health and safety problems, however, petroleum gas stations with inflammable substances, factories containing dust fibers, warehouses for storing dry inflammable substances and the like are common buildings for life and work, if the buildings are made of common concrete materials, sparks can be generated under the conditions of collision and friction, serious fire and explosion hidden dangers are caused, and the important factors threatening public safety are caused.

Non-ignitability means that when the material is subjected to mechanical action such as friction, impact or scouring with a hard substance such as metal or stone, sparks (or sparks) are not generated, so that the inflammable substance is in danger of igniting or exploding. Therefore, the direction of the unfired concrete to be controlled comprises two aspects, namely, the proportioning components are changed or raw materials are controlled, and the total quantity of static electricity generated by mechanical impact and friction of the concrete is reduced. The other is to reduce the concentration of static electricity, because when the static electricity is gathered to reach a certain energy, a spark will be generated, and when flammable gas, liquid and the like exist outside, the spark may become an ignition source factor causing combustion and explosion.

However, the quality of concrete only needs to consider strength, durability and non-ignitability, and the working performance is an important factor influencing the construction efficiency, quality and the quality of hardened concrete. If the concrete mixture can mainly depend on self weight, the model can be filled and paved on the ground without vibration, so that the labor cost of construction can be reduced, the construction progress can be accelerated, the construction quality is improved, and the prepared non-ignition concrete with self-compaction performance has better application value.

The self-compactness means that the concrete mixture has good construction performance and filling performance, is reliable in self weight, and can fill the model and be spread without vibration. The self-compaction performance of concrete is not only dependent on the fluidity of the mixture, and if the fluidity of the concrete mixture is improved, lower slurry viscosity and more slurry quantity are needed. At the moment, the low viscosity and rich slurry of the concrete mixture reduce the flow resistance of the aggregate in the concrete, so that segregation is generated, and the working performance of the concrete is influenced. Therefore, the difficulty with self-compacting concrete is in coordinating the contradiction between fluidity and stability.

Due to the special components and proportion of the non-ignition concrete, the non-ignition concrete is generally deficient in self-compacting performance at present. The invention aims to provide non-sparking self-compacting concrete with non-sparking performance and excellent self-compacting performance and a preparation method thereof, wherein the non-sparking self-compacting concrete has the non-sparking characteristic of the non-sparking concrete after impact and high working performance of the self-compacting concrete, and is special concrete with high application value.

Disclosure of Invention

The invention provides a preparation method of non-firing self-compacting concrete, aiming at solving the technical problem of poor self-compacting performance of the non-firing concrete in the prior art.

The technical scheme adopted by the invention is as follows: the preparation method of the non-ignition self-compacting concrete comprises the production raw materials of cement, mineral admixture, water, polyacrylonitrile-based carbon fiber, water reducer, dolomite coarse aggregate and dolomite fine aggregate. The single doping amount in the invention refers to: the raw material addition amount of the concrete mixture of each production party, for example, the single addition amount of the dolomite coarse aggregate is 756-810 kg, namely the addition amount of the concrete mixture dolomite coarse aggregate of each production party is 756-810 kg.

Although the unfired concrete in the prior art generally has the problem of poor self-compacting performance, the inventor tests and researches find that when dolomite is selected as unfired concrete coarse aggregate and fine aggregate and the proportion of the coarse aggregate and the fine aggregate is controlled, namely, the single-component mixing amount of the dolomite coarse aggregate is 756-810 kg, and the single-component mixing amount of the dolomite fine aggregate is 835-859 kg, the slurry in the mixture is rich, the flow resistance of the aggregate in the concrete is reduced, the coarse aggregate is filled, wrapped and lubricated by sufficient mortar amount, and the surface of the fine aggregate is wrapped by sufficient cement slurry, so that the friction between the aggregates is reduced, and the concrete mixture obtains better self-compacting performance.

As a further improvement of the invention, the dolomite coarse aggregate is continuously graded, and the maximum grain size is not more than 20 mm. The coarse aggregates with continuous gradation are selected, so that gaps among the aggregates are reduced, and redundant cement slurry forms a cement slurry layer among the aggregates, so that the slurry flowability is better. The maximum aggregate particle size of less than 20mm can reduce the yield shear stress of aggregate moving in the slurry, and is beneficial to the fluidity of concrete mixtures. Meanwhile, the smaller particle size reduces the settling velocity of the coarse aggregate in the slurry, and is also beneficial to maintaining the stability of the concrete.

As a further improvement of the invention, the production raw material also comprises hydroxyethyl cellulose, and the single component mixing amount of the hydroxyethyl cellulose is 0.5-0.7 kg.

At present, polyacrylonitrile-based carbon fibers are widely used in preparation of non-firing concrete, and the aim is to reduce static aggregation generated after concrete impact, when the static aggregation reaches certain energy, sparks can be generated, and flammable gas, liquid and the like exist outside the static aggregation, the static aggregation can possibly become an ignition source factor for causing combustion and explosion. In order to avoid static concentration, a conductive medium is required to be doped in the non-ignited concrete, a conductive net is formed in the concrete, when the non-ignited concrete is impacted, the formed conductive net conducts away electric charges concentrated at impact points, and the accidents of explosion, fire and the like seriously damaging safety due to the fact that the electric charges are concentrated to generate sparks are avoided.

However, the scheme has a great defect that the polyacrylonitrile-based carbon fibers are easy to form bundles, so that the working performance of the concrete is reduced, and the polyacrylonitrile-based carbon fibers cannot be dispersed in the concrete to form a conductive network, so that the non-ignition performance is unqualified. In order to solve the problem, the invention further increases the raw material of hydroxyethyl cellulose, and the single mixing amount is 0.5-0.7 kg. Experiments show that the scheme can obviously improve the agglomeration phenomenon of the polyacrylonitrile-based carbon fiber in the concrete slurry, not only can further improve the non-ignitability of the material, but also can improve the self-compactness of the material.

As a further improvement of the invention, the mineral admixture comprises fly ash and mineral powder, wherein the single blending amount of the fly ash is 86-102 kg, and the single blending amount of the mineral powder is 129-178 kg.

Experiments show that although the hydroxyethyl cellulose is added in the scheme, the agglomeration phenomenon of the polyacrylonitrile-based carbon fiber in the concrete slurry can be obviously improved, the addition of the hydroxyethyl cellulose causes the viscosity of a liquid phase to be increased, so that the mixed slurry has overlarge viscosity and is difficult to flow out. In order to solve the problem, hydroxyethyl cellulose is utilized, and simultaneously, a mineral admixture with a high mixing amount is adopted, wherein the mineral admixture comprises coal ash and mineral powder, the single mixing amount of the coal ash is 86-102 kg, and the single mixing amount of the mineral powder is 129-178 kg.

As a further improvement of the invention, the production raw materials comprise the following components in single mixing amount: 210-257 kg of cement, 86-102 kg of fly ash, 129-178 kg of mineral powder, 190-230 kg of water, 4.5-5.5 kg of polyacrylonitrile-based carbon fiber, 0.5-0.7 kg of hydroxyethyl cellulose, 7.7-9.2 kg of a water reducing agent, 756-810 kg of dolomite coarse aggregate and 835-859 kg of dolomite fine aggregate.

As a further improvement of the invention, the single-component total mixing amount of the cement, the fly ash and the mineral powder is 431-509 kg.

As a further improvement of the invention, the dolomite fine aggregate is machine-made sand obtained by crushing dolomite, and the fineness modulus is 2.5-2.8. The reason that the machine-made sand obtained after crushing the dolomite is the fine aggregate is that the common machine-made sand has lower hardness and lower impurities because the hardness and the metal-containing impurities of the common machine-made sand cannot meet the requirement of the non-ignition performance of the concrete. In addition, the dolomite sand has smooth surface, small water adsorption, fineness modulus of 2.5-2.8 and smaller particle size, reduces friction among coarse aggregates in concrete mixture and is beneficial to self-compaction performance of concrete.

As a further improvement of the invention, the water demand ratio of the fly ash is not more than 95 percent, and the specific surface area is more than 400m²Per kg, the specific surface area of the mineral powder is more than 400m²Kg, fluidity ratio greater than 95%.

As a further improvement of the invention, the water reducing agent is a polycarboxylic acid water reducing agent, the solid content of the polycarboxylic acid water reducing agent is 20%, and the water reducing rate is more than 25%.

As a further improvement of the invention, the preparation method of the non-firing self-compacting concrete specifically comprises the following steps:

s1: weighing the raw materials according to the mixing amount of the raw materials in the claim 5;

s2: carrying out magnetic separation on the dolomite coarse aggregate and the dolomite fine aggregate to remove iron in the dolomite coarse aggregate and carrying out a non-ignition test, and putting cement, fly ash, mineral powder, dolomite fine aggregate and dolomite coarse aggregate into a stirrer after the test is qualified;

s3: taking half of the weight of water, and dissolving a water reducing agent in the water to obtain a water reducing agent aqueous solution;

s4: putting the other half weight of water into a container, putting polyacrylonitrile-based carbon fiber into the water, pre-dispersing the fiber for 1min by adopting 200-400W ultrasonic wave, adding hydroxyethyl cellulose, and continuing to perform ultrasonic dispersion for at least 2min to obtain a dispersed polyacrylonitrile-based carbon fiber aqueous solution;

s5: and (2) dry-mixing cement, fly ash, mineral powder, dolomite fine aggregate and dolomite coarse aggregate in a mixer for at least 1min, then adding the water reducing agent aqueous solution while stirring, then adding the dispersed polyacrylonitrile-based carbon fiber aqueous solution, and continuously stirring for at least 2min to obtain the acrylic fiber/polyacrylonitrile fiber composite material.

In the scheme S4, a first doping method is adopted, polyacrylonitrile-based carbon fibers are placed in water for ultrasonic dispersion, and then a dispersing agent is combined with ultrasonic dispersion, so that the dispersibility of the carbon fibers can be effectively improved.

In S5, the cement, the fly ash, the mineral powder, the dolomite fine aggregate and the dolomite coarse aggregate are firstly dry-mixed and mixed, and the raw materials are evenly mixed. Adding polyacrylonitrile-based carbon fiber and part of water, and then adding a polycarboxylate water reducer aqueous solution, wherein the surface of the polyacrylonitrile-based carbon fiber contains polar carbonyl and carboxyl groups, and if the water reducer and the polyacrylonitrile-based carbon fiber are added simultaneously, the polycarboxylate water reducer is adsorbed on the surface of the carbon fiber, so that the polycarboxylate water reducer molecules acting on cement particles are reduced. Therefore, part of the polycarboxylic acid admixture is dissolved in water and mixed, then the polycarboxylic acid admixture is mixed with concrete for 1min, the polycarboxylic acid admixture is mixed with the dispersion liquid of polyacrylonitrile-based carbon fibers and water after reacting with the cement, and then the polyacrylonitrile-based carbon fibers and the dispersion liquid of the water are mixed with the concrete, so that the carbon fibers can be mixed more uniformly, the phenomenon that the action effect of the water reducing agent is weakened due to the adsorption of the polycarboxylic acid water reducing agent by the carbon fibers can be reduced, and the self-compaction performance of concrete mixture slurry is ensured.

More preferably, the polyacrylonitrile-based carbon fiber is a chopped fiber having a length of 6mm, a monofilament particle diameter of 7.3 μm, and a linear density of 0.79g · m^-1The tensile modulus was 231 GPa.

More preferably, the cement is ordinary portland cement.

The invention also discloses the non-ignition self-compacting concrete which is prepared by the preparation method of the non-ignition self-compacting concrete.

The invention has the beneficial effects that: 1) the self-compaction of the non-ignition concrete mixture is obviously improved by adopting the technical scheme that the single mixing amount of the dolomite coarse aggregate is 756-810 kg, and the single mixing amount of the dolomite fine aggregate is 835-859 kg; 2) the self-compaction of the material is further improved by using continuous graded dolomite coarse aggregate with the maximum grain diameter not more than 20 mm; 3) by using the hydroxyethyl cellulose, the agglomeration phenomenon of the polyacrylonitrile-based carbon fiber in the concrete slurry is obviously improved, so that the non-ignitability of the material can be further improved, and the self-compactness of the material can be improved; 4) the method adopts the fly ash and the mineral powder with higher mixing amount, wherein the single mixing amount of the fly ash is 86-102 kg, and the single mixing amount of the mineral powder is 129-178 kg, so that the viscosity of slurry is effectively controlled, and the increase of the viscosity of a liquid phase is avoided. 5) The method comprises the steps of mixing and stirring part of water and the water reducing agent with the cementing material and the aggregate concrete, and then mixing and stirring the water and the polyacrylonitrile-based carbon fibers dispersed in the water, so that the dispersibility of the carbon fibers can be effectively improved, and the negative influence of the carbon fibers on the self-compaction performance of the concrete mixture is reduced.

Detailed Description

The present invention will be further described with reference to the following examples.

The first embodiment is as follows:

(1) weighing the raw materials according to the following single mixing amount proportion:

wherein the cement is P.O II 42.5R ordinary portland cement, and the specific surface area is 373m²The initial setting time is 170min, the final setting time is 256min, the three-day compressive strength is 31.2MPa, and the 28d compressive strength is 50.1 MPa.

The dolomite coarse aggregate is natural dolomite, CaCO₃The content is 96.7%, and the grain size is 5-20 mm.

The fine aggregate is machine-made sand obtained by crushing natural dolomite, the content of stone powder is 8 percent, and the fineness modulus is 2.67.

The fly ash is F-class I-grade fly ash, the water requirement ratio is 95%, and the specific surface area is 430m²The mineral powder is S95 grade mineral powder with a specific surface area of 435 m/kg²/kg。

The polyacrylonitrile-based carbon fiber is a chopped fiber with the length of 6mm, the monofilament particle size is 7.3 mu m, and the linear density is 0.79 g.m^-1The tensile modulus was 231 GPa.

The polycarboxylate superplasticizer is a Hedera helix SSJS standard high-performance water reducer, the solid content is 20%, and the water reducing rate is more than 25%.

(2) Carrying out magnetic separation on the dolomite coarse aggregate and the dolomite fine aggregate to remove iron in the dolomite coarse aggregate and carrying out a non-ignition test, and putting cement, fly ash, mineral powder, dolomite fine aggregate and dolomite coarse aggregate into a stirrer after the test is qualified;

(3) taking half of the weight of water, and dissolving a polycarboxylic acid water reducing agent in the water to obtain a water reducing agent aqueous solution;

(4) putting the other half weight of water into a container, putting the polyacrylonitrile-based carbon fiber into the water, pre-dispersing the fiber for 1min by adopting 300W ultrasonic wave, adding hydroxyethyl cellulose, and continuing to perform ultrasonic dispersion for 2min to obtain a dispersed polyacrylonitrile-based carbon fiber aqueous solution;

(5) and (2) dry-mixing cement, fly ash, mineral powder, dolomite fine aggregate and dolomite coarse aggregate in a mixer for 1min, then adding the water reducing agent aqueous solution while stirring, adding the dispersed polyacrylonitrile-based carbon fiber aqueous solution after 1min, and continuously stirring for 2min to obtain the acrylic fiber/polyacrylonitrile fiber composite material.

Example two:

the design is carried out according to the same conditions as the first embodiment, and the difference is only that: weighing the raw materials according to the following single mixing amount proportion:

example three:

example four:

example five:

example six:

example seven:

example eight:

comparative example one:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: the single blending amount of the dolomite coarse aggregate is 876kg, and the single blending amount of the dolomite fine aggregate is 739 kg.

Comparative example two:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: the single mixing amount of the dolomite coarse aggregate is 735kg, and the single mixing amount of the dolomite fine aggregate is 880 kg.

Comparative example three:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: the maximum particle size of the coarse aggregate rises to 30 mm.

Comparative example four:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: hydroxyethyl cellulose was not used.

Comparative example five:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: the single mixing amount of the cement, the fly ash and the mineral powder is 391kg, 34kg and 63kg respectively.

Comparative example six:

this comparative example is a control experiment of example two, designed under the same conditions as example two, except that: the single mixing amount of the cement, the fly ash and the mineral powder is respectively 130kg, 183kg and 209 kg.

Detection method

The concrete mixtures of the examples and the comparative examples are subjected to self-compaction performance test, then are placed in a 100mm multiplied by 100mm mould, are stood in a room temperature environment for 1 day, are demoulded and are placed in a standard curing box for curing to the age of 28 days, and the test block is subjected to non-ignition performance test.

The self-compaction performance detection mainly comprises slump expansion degree, expansion time and J-ring difference, and the specific test method is executed according to JGJT283-2012 'technical specification for self-compaction concrete application'.

The method for testing the non-ignition performance comprises the following steps: the method comprises the steps of firstly determining whether a grinding wheel for testing is qualified or not by using the grinding wheel, carrying out friction inspection on the grinding wheel in a completely dark room, controlling the rotating speed of the grinding wheel at 1000r/min, adding 20N pressure during friction, carrying out friction by using quartzite, and if clear sparks occur, determining that the grinding wheel is qualified and can be used for a non-ignition test. 10 samples with the mass of 50-250 g, different surfaces, different colors, different crystals and different hardness are selected from the dolomite aggregate, and a non-ignition test of the coarse aggregate is carried out in a completely dark room. When the aggregate is rubbed with the grinding wheel, carefully observing whether sparks occur at the place where the test piece is rubbed with the grinding wheel, stopping the test until each test piece is ground to be not less than 20g, recording whether sparks are found in the test process, and judging that the material is a non-sparking material if no instantaneous sparks are found in the test process. The concrete material was tested using 100mm x 100mm test pieces. The results of the tests of the examples and comparative examples are shown in Table 1.

Table 1: test result table for self-sealing and non-firing performance of concrete material

As can be seen from Table 1, the concrete materials prepared in examples one to eight all have slump spreads of more than 660mm, which reach SF2 grade or above. The J-ring differential test shows that the prepared concrete mixture has good ability to penetrate through the steel bars. 3d, 7d and 28d compressive strength tests show that the strength of the prepared non-sparking self-compacting concrete reaches above C30. In conclusion, the prepared non-sparking self-compacting concrete has excellent non-sparking performance and good self-compacting performance.

It can also be seen from the comparative examples I and II in Table 1 that when the single blending amount of the dolomite coarse aggregate and the dolomite fine aggregate of the present invention is changed, resulting in a numerical range not falling within the numerical range of the present invention, the slump spread of the material is reduced from 725 to 630 and 675, respectively, which illustrates the technical effect of the present invention of significantly improving the self-compaction of the non-firing concrete.

It can also be seen from the third comparative example in table 1 that the larger particle size of the coarse aggregate results in difficulty in moving within the slurry, ease of settling and reduced self-compaction of the concrete mix.

It can also be seen from the fourth comparative example in table 1 that the use of hydroxyethyl cellulose can significantly improve the caking phenomenon of polyacrylonitrile-based carbon fibers in concrete slurry, not only can further improve the non-ignitability of the material, but also can ensure the self-compactness of the material.

As can be seen from the fifth comparative example in Table 1, when the amount of the mineral admixture used is less than the amount of the mineral admixture of the present invention, the self-compaction of the material is remarkably reduced because the hydroxyethyl cellulose is contained in the raw material, and the addition of the hydroxyethyl cellulose causes the viscosity of the liquid phase to increase, so that the viscosity of the mixed slurry is too high to flow out. The mineral admixture provided by the invention can effectively control the viscosity of slurry and avoid the increase of the liquid phase viscosity, thereby improving the self-compactness of the material.

As can be seen from the sixth comparative example in Table 1, when the amount of the mineral admixture used exceeds the amount of the mineral admixture of the present invention, the cement content in the cementitious material is low, which results in lower strength of 3d, 7d and 28d of concrete, and the strength requirement of C30 concrete is difficult to meet.

Claims

1. The preparation method of the non-ignition self-compacting concrete comprises the following raw materials in single mixing amount: 210-257 kg of cement, 86-102 kg of fly ash, 129-178 kg of mineral powder, 190-230 kg of water, 4.5-5.5 kg of polyacrylonitrile-based carbon fiber, 0.5-0.7 kg of hydroxyethyl cellulose, 7.7-9.2 kg of a water reducing agent, 756-810 kg of dolomite coarse aggregate and 835-859 kg of dolomite fine aggregate.

2. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the dolomite coarse aggregate is in continuous gradation, and the maximum grain size is not more than 20 mm.

3. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the single-component total mixing amount of the cement, the fly ash and the mineral powder is 431-509 kg.

4. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the dolomite fine aggregate is machine-made sand obtained by crushing dolomite, and the fineness modulus is 2.5-2.8.

5. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the water demand ratio of the fly ash is not more than 95 percent, and the specific surface area is more than 400m²Per kg, the specific surface area of the mineral powder is more than 400m²Kg, fluidity ratio greater than 95%.

6. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the water reducing agent is a polycarboxylate water reducing agent, the solid content of the polycarboxylate water reducing agent is 20%, and the water reducing rate is more than 25%.

7. The method for preparing a nonflammable self-compacting concrete according to claim 1, wherein: the method comprises the following steps:

s1: weighing the raw materials according to the mixing amount of the raw materials in claim 1;

8. The nonflammable self-compacting concrete prepared by the method for preparing the nonflammable self-compacting concrete according to any one of claims 1 to 7.